Japanese Published Patent Application No 10-201206 shows a stator for an electric motor. The stator comprises a housing with two arcuate sides and two magnetic poles. Each magnetic pole is composed of one large arcuate magnet which is fixed to an inner surface of a corresponding arcuate side of the housing.
However, the manufacture of large arcuate magnets is complicated. The arcuate magnets are formed as rectangular magnets which are then cut to shape. Thus there is a lot of material wastage plus there are breakages when cutting the magnets resulting in a low efficiency of material usage.